Day: January 24, 2013

[James] has been building a heart rate monitor using a very cool TI chip. He needed a way to test his device, and commercial ECG simulators, like all biotech devices, are absurdly expensive. [James] decided to build his own heart rate simulator, and in the process made a great tool and one of the most well documented projects we’ve ever seen.

Of course, if you’re building an ECG simulator, you’re going to need a good sample of a heart’s electrical pattern. To get this sample, [James] found an old army manual with a diagram of an ideal ECG pattern. [James] took this PDF manual, screen capped the diagram, and used a Python script to generate an array in C the Arduino could repeat over and over.

The rest of the build consisted of a D/A converter, a pot to change the heart rate, a very nice seven-segment display, and a few banana jacks to connect to [James]’ heart monitor. Everything is up in a git, including an amazingly well documented (87 pages!) tutorial for building your own Arduino heart simulator.

Take a gander at the part of this extruder head which looks like a chess pawn. It’s the mounting bracket for the hot end and it’s made out of ceramic. [Ed] came up with the idea to use ceramic to mount the hot end when trying to improve the design while keeping it rather simple and easy to assemble. The concept uses the thermal properties of the ceramic to insulate well enough to operate the extruder at higher temperatures without causing other problems.

Where does one get a custom ceramic part anyway? Turns out you can get low volume runs from China much like PCBs. The minimum order was ten units, which was still a leap of faith since he had no way of testing the design in advance. The first run with the new part went quite well, but only for the first layer and then the filament jammed. He’s still not sure why, but overcame the issue by lining the inside of the ceramic with a PTFE tube. This means he now has to use a smaller filament to fit through it. But the quality of the prints he’s getting with 1.75mm stock and the ceramic head are superb.